CVE-2026-78212: 4MOSAn Path Traversal Vulnerability

CVE-2026-78212 Overview

CVE-2026-78212 is a relative path traversal vulnerability [CWE-23] in 4MOSAn, developed by 4MOSAn Security Technology Co., Ltd. The flaw allows unauthenticated remote attackers to read arbitrary files from the underlying operating system. Attackers exploit the issue over the network without user interaction or prior credentials. TW-CERT published advisories describing the weakness and its impact on affected 4MOSAn deployments.

Critical Impact
Unauthenticated remote attackers can download arbitrary system files, exposing configuration data, credentials, and sensitive application content.

Affected Products

4MOSAn (vendor: 4MOSAn Security Technology Co., Ltd.)
Specific affected versions were not enumerated in the NVD record at publication
Refer to TW-CERT advisories for the authoritative version list

Discovery Timeline

2026-08-24 - CVE-2026-78212 published to the National Vulnerability Database
2026-08-26 - Last updated in NVD database

Technical Details for CVE-2026-78212

Vulnerability Analysis

The vulnerability is a Relative Path Traversal issue classified under [CWE-23]. The 4MOSAn application accepts a file path parameter that is used to construct a filesystem read operation. The application fails to normalize or restrict traversal sequences such as ../ before resolving the path. As a result, an attacker can escape the intended directory and reach arbitrary files on the host.

Exploitation requires no authentication and no user interaction. An attacker sends a crafted HTTP request that references a target file using relative path components. The application returns the file contents in the response. This exposes sensitive data including application configuration files, credentials, session tokens, and operating system files readable by the service account.

Root Cause

The root cause is insufficient input validation on a user-supplied file path. The application does not canonicalize the path or enforce a strict allowlist of permitted directories. Traversal characters bypass the intended download boundary and reach the underlying filesystem.

Attack Vector

The attack vector is network-based. An unauthenticated attacker submits an HTTP request containing traversal sequences in a filename or path parameter. The vulnerability affects confidentiality only; integrity and availability are not directly impacted. See the TW-CERT Advisory #11123 and TW-CERT Advisory #11119 for further technical detail.

No verified proof-of-concept code has been published. The vulnerability mechanism follows the standard relative path traversal pattern where sequences such as ../../../../etc/passwd or Windows equivalents like ..\..\..\windows\win.ini are appended to a file-download endpoint parameter.

Detection Methods for CVE-2026-78212

Indicators of Compromise

HTTP requests to 4MOSAn endpoints containing ../, ..\, or URL-encoded variants such as %2e%2e%2f and %2e%2e%5c
Requests referencing sensitive system paths such as /etc/passwd, /etc/shadow, web.config, or boot.ini
Anomalous outbound file download volumes from the 4MOSAn service account
Web server access logs showing unauthenticated requests returning HTTP 200 with large response bodies

Detection Strategies

Deploy web application firewall rules that block path traversal patterns in URL parameters and POST bodies targeting 4MOSAn endpoints
Inspect HTTP request parameters for encoded and double-encoded traversal sequences
Correlate unauthenticated read activity with subsequent authentication attempts using disclosed credentials
Baseline normal file access patterns for the 4MOSAn service and alert on deviations

Monitoring Recommendations

Enable verbose access logging on all 4MOSAn management interfaces
Forward web server and application logs to a centralized SIEM for retention and correlation
Alert on repeated 4xx or 5xx responses that indicate traversal probing
Monitor filesystem access by the 4MOSAn process for reads outside the expected data directory

How to Mitigate CVE-2026-78212

Immediate Actions Required

Restrict network access to 4MOSAn management interfaces to trusted administrative networks
Apply the vendor patch referenced in the TW-CERT advisories as soon as it is available for your version
Rotate any credentials, API keys, or secrets that may have been readable from the filesystem
Review web server and application logs for prior traversal attempts dating back several months

Patch Information

Consult the TW-CERT Advisory #11123 and TW-CERT Advisory #11119 for the vendor-supplied fixed versions and upgrade guidance. Contact 4MOSAn Security Technology Co., Ltd. directly for private patch distributions if applicable.

Workarounds

Place the 4MOSAn application behind a reverse proxy or WAF that blocks path traversal payloads
Enforce network segmentation so the affected service cannot be reached from untrusted networks
Run the 4MOSAn service under a least-privilege account to limit the scope of readable files
Remove or protect sensitive files from directories accessible to the service account until the patch is applied

bash

# Example nginx rule to block common traversal patterns upstream of 4MOSAn
location / {
    if ($request_uri ~* "(\.\./|\.\.\\|%2e%2e%2f|%2e%2e%5c)") {
        return 403;
    }
    proxy_pass http://4mosan_backend;
}